In a recent a micro-process, an irregular pattern (e.g., resist pattern) is generally formed on a substrate (e.g., semiconductor wafer) by means of a photolithographic technique. Specifically, the irregular pattern is formed by a coating step for coating a substrate with a resist material to form a resist film, an exposure step for exposing the resist film, and a developing step for developing the exposed resist film.
The developing step includes a cleaning process in which a substance of a dissolved resist (dissolved resist substance), which has been dissolved by a developer, is removed together with the developer from a surface of the substrate. In the cleaning process, if the resist dissolved substance is not completely removed to remain on the substrate, a desired irregular pattern may not be obtained, resulting in defective development.
Thus, in order to restrain the defective development, a substrate cleaning method described in JP2006-080315A includes: a step in which a cleaning liquid is supplied to a central portion of a rotating substrate so that the cleaning liquid spreads all over a surface of the substrate; a step in which, during the rotation of the substrate, a cleaning-liquid supply position on the surface of the substrate is moved from a central side of the substrate toward a peripheral side thereof by a predetermined distance, and a dry gas is ejected to the central portion of the substrate to form a dry area; and a step in which, during the rotation of the substrate, the cleaning-liquid supply position on the surface of the substrate is further moved toward the peripheral side of the substrate. In this case, along with the movement of the cleaning-liquid supply position on the surface of the substrate, the dry area formed on the central portion of the substrate spreads outward by an action of the centrifugal force. Thus, the cleaning liquid is discharged outward from recesses in the irregular pattern, and the resist dissolved substance is discharged together with the cleaning liquid. As a result, occurrence of the defective development can be restrained.